U.S. Pat. No. 4,951,774 of Buell discloses a dual tank motorcycle fuel tank with a forked configuration, wherein the forked fuel tank is built into the motorcycle frame.
A motorcycle frame with an integral fuel tank is also disclosed in U.S. Pat. No. 6,484,837, also of Buell.
U.S. Pat. No. 3,252,537 of Tarran discloses a single motorcycle fuel tank in a tubular frame.
U.S. Pat. No. 906,417 of Harman also discloses a single motorcycle fuel tank in a tubular frame.
U.S. Pat. No. 4,461,489 of Tsukiji discloses a body frame with a single integral motorcycle fuel tank.
U.S. Pat. No. 4,585,086 of Hiramatsu and U.S. Pat. No. 4,311,261 of Anderson discuss motorcycle frames in general.
Additionally, rotatable steering systems are known in four wheeled motor vehicles, such as automobiles and trucks.